Coaxial cables comprising a coaxial element wire, made up of a center conductor, an insulation layer, and an outer conductor, and a jacket disposed over the coaxial element wire, are known. Included among the types of coaxial cables are a single-core cable formed by providing a single coaxial element wire with a jacket, a multicore cable formed by providing a plurality of single-core cables with a common jacket, and a multicore cable formed by providing a plurality of coaxial element wires with a common jacket. Included among the types of arrangements of coaxial element wires or single-core cables in a multicore cable are a flat-type multicore cable obtained by arranging coaxial element wires or coaxial cables on a plane, and a twisted-layer multicore cable obtained by twisting them together. There are cases where the same type of cables are combined in such a single-core or multicore coaxial cable and where different types, such as communication wires, power wires, and the like, are compounded therein to provide a compound cable.
In the conventional coaxial cables, a metallic tape or a laminate tape obtained by laminating a metallic tape and an insulating film of polyester or the like is generally used as the outer conductor (shield). A braided structure of metallic tapes as disclosed in Japanese Laid-open Utility Model No. Hei 2-47726 and No. Hei 2-47728 is known. The advantage of the outer conductor when it is formed of braided metal tapes is that it does not become loose. On the other hand, its disadvantage is that removal of the outer conductor is troublesome when, for example, making a terminal treatment.
FIG. 4 is a side view showing a conventional coaxial cable employing braided metallic tapes. Referring to FIG. 4, reference numeral 11 denotes a center conductor, 12 denotes an insulation layer, 13 denotes an outer conductor formed by braiding metallic tapes, and 14 denotes a jacket. Metallic tapes obtained by slitting a wide metallic tape are normally used.
However, at the time of slitting the metallic tape, sharp edges such as burrs are produced on the cut surface and such edge portions can injure the insulation layer 12 or cause a voltage concentration on that portion thereby decreasing the dielectric strength of the insulation layer 12.
This problem becomes serious especially when a small-diameter coaxial cable whose insulation layer thickness is as small as 0.15 mm or less is used.
Further, when a conventional coaxial cable is used for connecting devices within an electronic apparatus, especially when it is used in a notebook computer at the rotating portion where the monitor portion and the main body portion are connected, or when it is disposed at the moving portion of a diagnostic sensor cable which moves when changing examined parts of the body, there arises a problem of electrostatic noises produced by friction between the insulation layer 12 and the outer conductor 13 of the moving coaxial cable.